Buying a HW, a HW i actually already own, twice is always a bad deal. (tough for Sony it also is/was)

I wonder sometimes how many of those 40 resp. 35 mio consoles sold are for similar purposes. A backup machine, an exchange unit for RRoD/YLoD after warranty period or a Box for being banned from Live.
Is this a new way to boost sales or did this already happen in previous generations?